Run-flat tire

ABSTRACT

The run flat tire includes a tread portion in contact with a road surface, a tire side portion continuous to the tread portion and positioned inside in the radial direction of the tread portion, and a carcass forming a tire skeleton. The run flat tire is provided with a side reinforcing rubber in tire side portion. A carcass reinforcing belt formed by covering a circumferential direction cord extending along tire circumferential direction with a rubber material and a sheet-like reinforcing layer formed of a resin material are provided in layers on an inner side of the tire radial direction of the tread portion.

TECHNICAL FIELD

The present invention relates to a run-flat tire having a carcassreinforcing belt formed by covering a circumferential direction cordwith a rubber material.

BACKGROUND ART

Conventionally, a run-flat tire having a carcass reinforcing belt(called a crown reinforcing member) for reinforcing a carcass forming atire skeleton has known. The carcass reinforcing belt is provided insidea tire radial direction of a tread portion contacting a road surface(see Patent Literature 1). The carcass reinforcing belt is formed bycovering a circumferential direction cord extending to a tirecircumferential direction with a rubber material.

Since the carcass reinforcing belt is provided as an alternative to thestandard crossing belt layer, the crossing belt layer is not provided intire disclosed in Patent Literature 1.

In the tire disclosed in Patent Literature 1, a sheet-like reinforcinglayer formed of a resin material is provided outside a tire radialdirection of a carcass reinforcing belt. Specifically, the reinforcinglayer is formed of a thermoplastic polymer film. It is believed thatsuch a reinforcing layer advantageously affects cornering rigidity ofthe tire.

CITATION LIST Patent Literature

Patent Literature 1 Japanese Unexamined Patent Application PublicationNo. 2016-193725

SUMMARY OF INVENTION

In the case of tire provided with the carcass reinforcing belt in whichthe circumferential direction cord is covered with a rubber material asdescribed above, it is conceivable that there are the following problemswhen the run-flat traveling is to be realized.

Specifically, it is considered difficult to sufficiently suppress thebuckling during run-flat traveling in the combination of theabove-described carcass reinforcing belt and the sheet-like reinforcinglayer formed of a resin material, rather than in the case of a standardcrossing belt layer.

Accordingly, an object of the present invention is to provide a run-flattire capable of more reliably suppressing a buckling when a carcassreinforcing belt having a circumferential direction cord extending totire circumferential direction covered with a rubber material and asheet-like reinforcing layer formed of a resin material are providedinside a tire radial direction of a tread portion.

One aspect of the present invention is a run-flat tire including a treadportion in contact with a road surface, a tire side portion continuousto the tread portion and positioned inside in the tire radial directionof the tread portion, and a carcass that forms tire skeleton. A sidereinforcing rubber is provided in the tire side portion, and on an innerside of a tire radial direction of the tread portion, a carcassreinforcing belt in which a circumferential direction cord extendingalong tire circumferential direction is covered with a rubber materialand a sheet-like reinforcing layer formed of a resin material areprovided in a layer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a run flat tire 10.

FIG. 2 is a partially enlarged cross-sectional view of the run flat tire10.

FIG. 3 is an exploded plan view of a portion of the run-flat tire 10.

FIG. 4 is a partially enlarged cross-sectional view of a run flat tire10 A.

FIG. 5 is a partially enlarged cross-sectional view of a run flat tire10 B.

FIG. 6 is a partially enlarged cross-sectional view of a run flat tire10 C.

FIG. 7 is a partially enlarged cross-sectional view of a run flat tire10 D.

DESCRIPTION OF EMBODIMENTS

Embodiments will be described below with reference to the drawings. Thesame functions and configurations are denoted by the same or similarreference numerals, and descriptions thereof are omitted as appropriate.

(1) Overall structure of tire

FIG. 1 is a sectional view of the run-flat tire 10 according to thepresent embodiment. Specifically, FIG. 1 is a cross-sectional view ofthe run flat tire 10 along tire width direction and tire radialdirection. The run flat tire 10 has a mostly symmetrical shape withrespect to tire equatorial line CL.

In FIG. 1, the sectional hatching is not shown (hereinafter the same).In order to facilitate the differentiation of similar components, aschematic pattern is shown for some components.

The run-flat tire 10 is capable of running (run flat running) at aconstant speed for a certain distance (80 km at 80 km/h) even when theinternal pressure (air pressure) is significantly reduced due to apuncture or the like (e.g., 0 kPa).

As shown in FIG. 1, the run flat tire 10 includes a tread portion 20, atire side portion 30, a carcass 40, a carcass reinforcing belt 50, abead portion 60, a side reinforcing rubber 70, a reinforcing layer 80,and a width direction treat 90.

The tread portion 20 is a part in contact with a road surface (notshown). On the tread portion 20, a pattern (not shown) corresponding tothe use environment of the run-flat tire 10 and the type of vehicle tobe mounted is formed.

The tire side portion 30 continues to the tread portion 20 and ispositioned inside in the tire radial direction of the tread portion 20.The tire side portion 30 is a region from the tire width directionoutside end of the tread portion 20 to the upper end of the bead portion60. The tire side portion 30 is sometimes referred to as a side wall orthe like.

The carcass 40 forms a skeleton (tire skeleton) of a run-flat tire 10.The carcass 40 has a radial structure in which carcass cords 41 (notshown in FIG. 1, see FIG. 3) arranged radially along a tire radialdirection is covered with a rubber material. However, the presentinvention is not limited to a radial structure, and a bias structure inwhich the carcass cords 41 are arranged so as to cross each other in thetire radial direction may be used.

The carcass cord 41 is not particularly limited, and may be formed of anorganic fiber cord in the same manner as a tire for a standard passengercar (including minivans and SUV (Sport Utility Vehicles)).

The carcass reinforcing belt 50 is provided inside the tire radialdirection of the tread portion 20. The carcass reinforcing belt 50 isprovided mainly for reinforcing the carcass 40. In this embodiment, thecarcass reinforcing belt 50 is a belt that replaces the conventionalstandard crossing belt layer. Therefore, the run flat tire 10 is notprovided with a crossing belt layer.

The carcass reinforcing belt 50 has a circumferential direction cord 51covered with a rubber material.

Specifically, the circumferential cord 51 extends along the tirecircumferential direction. The term “extending along the tirecircumferential direction ” includes a state in which thecircumferential direction cord 51 is disposed in parallel with tirecircumferential direction and a state in which the circumferentialdirection cord 51 is disposed so as to be inclined to form an angle ofwithin ±10 degrees with respect to tire circumferential direction.

The circumferential direction cord 51 may be formed of a metal cord,such as steel, or an organic fiber cord, such as aramid.

Also, the circumferential direction cords 51 may be disposed at aplurality of substantially constant distances in the tire widthdirection or may be a single cord spirally wound along the tirecircumferential direction. The rubber material covering thecircumferential direction cord 51 can be the same as, for example, therubber material used for the carcass 40 or the rubber material used fora standard crossing belt layer.

Further, the shape of the carcass reinforcing belt 50 may be a spiralbelt which covers one or more circumferential direction cords 51 and iscut to a predetermined width, or may be a plurality of strip-like beltswhich are arranged inclined with respect to the tire circumferentialdirection. Alternatively, the shape of the carcass reinforcing belt 50may be an annular belt provided from one shoulder portion to the othershoulder portion of the tread portion 20.

The bead portion 60 continues to tire side portion 30 and is positionedinside in tire radial direction of tire side portion 30. The beadportion 60 is an annular shape extending to the tire circumferentialdirection.

The bead portion 60 is locked to a flange portion 110 (not shown in FIG.1, see FIG. 2) formed at the radially outside end of the rim wheel 100.

The side reinforcing rubber 70 is provided in the tire side portion 30.The side reinforcing rubber 70 has a crescent shape in cross section,and supports a load of a vehicle (not shown) to which the run-flat tire10 is mounted when the internal pressure of the run-flat tire 10 greatlydecreases.

The side reinforcing rubber 70 may be formed of one or more kinds ofrubber materials, or may contain other materials (short fiber, resin,etc.) if the rubber material is a main component.

The reinforcing layer 80 is provided outside the tire radial directionof the carcass reinforcing belt 50. The reinforcing layer 80 is formedof a resin material and has a sheet-like shape.

The reinforcing layer 80 may be formed of, for example, a thermoplasticpolymer. Specifically, a thermoplastic polymer film (multiaxiallyoriented film) that is stretched or oriented in two or more directionscan be used. The thermoplastic polymer film at least has a tensileelastic modulus greater than at least 500 MPa, and preferably has atensile elastic modulus greater than 2,000 MPa, regardless of thetensile direction.

The reinforcing layer 80 may not necessarily be formed of athermoplastic polymer, but may be formed of a thermosetting polymerhaving a crosslinked structure.

The width direction treat 90 is provided inside the tire radialdirection of the carcass reinforcing belt 50. The width direction treat90 has a predetermined width in the tire width direction. The widthdirection treat 90 is a rubber treat obtained by covering a widthdirection cord 91 (not shown in FIG. 1, see FIG. 3) extending to thetire width direction with a rubber material.

The width direction treat 90 can be formed of the same kind of rubber asrubber used for forming the carcass 40 or rubber used for forming a beadfiller 62 (not shown in FIG. 1, see FIG. 2).

In the run flat tire 10, the carcass reinforcing belt 50, thereinforcing layer 80 and the width direction treat 90 are provided inlayers at the inside of the tread portion 20 in the tire radialdirection.

(2) Detailed structure of inside tire radial direction of tread portion

FIG. 2 is a partially enlarged sectional view of the run-flat tire 10.Specifically, FIG. 2 is a partially enlarged sectional view of therun-flat tire 10 taken along the tire width direction and the tireradial direction. FIG. 3 is a partially exploded plan view of therun-flat tire 10.

As shown in FIGS. 2 and 3, the bead portion 60 has a bead core 61 andthe bead filler 62. In this structure example, the bead core 61 has apopular configuration and is formed by twisting a plurality of metalcords formed of steel or the like.

The bead filler 62 is a reinforcing member filled in a gap between thecarcasses 40 folded back via the bead core 61, and is formed by using arubber member harder than other parts.

The bead portion 60 may comprise a bead core formed by covering a metalcord with a resin material or a bead core formed by using a resinmaterial.

In the run flat tire 10, the reinforcing layer 80, the carcassreinforcing belt 50 and the width direction treat 90 are stacked fromoutside to inside of the tire radial direction.

The reinforcing layer 80 is in contact with the carcass reinforcing belt50. The width direction treat 90 is also in contact with the carcassreinforcing belt 50. Thus, a three-layer structure of the reinforcinglayer 80, the carcass reinforcing belt 50 and the width direction treat90 is formed.

The carcass reinforcing belt 50 may or may not contact the carcass 40. Arubber or the like forming the tread portion 20 or the tire side portion30 may be substantially partially interposed between the carcassreinforcing belt 50 and the reinforcing layer 80 and between the carcassreinforcing belt 50 and the width direction treat 90.

The reinforcing layer 80 does not have any particular cords and is anannular seat along tire circumferential direction. The widthwise treat90, on the other hand, has a width direction cord 91 extending to thetire width direction.

It should be noted that the portion extending to the tire widthdirection may be substantially along the tire width direction, and maybe so long as the width direction cord 91 is not along the tirecircumferential direction. Specifically, the angle between the widthdirection cord 91 and the tire width direction is preferably 0 to 60degrees.

The width direction cord 91 may be formed of a metal material, such assteel, or an organic fiber, such as Kevlar, nylon, or polyethyleneterephthalate (PET).

(3) Modified Example

Next, modified example of the run flat tire 10 will be described. Theparts different from the run-flat tire 10 will be mainly describedbelow.

(3.1) Modified Example 1

FIG. 4 is a partially enlarged sectional view of the run flat tire 10 A.As shown in FIG. 4, the run-flat tire 10 A, like the run-flat tire 10,includes the carcass reinforcing belt 50, the reinforcing layer 80, andthe width direction treat 90.

In the run flat tire 10 A, the carcass reinforcing belt 50, thereinforcing layer 80 and the width direction treat 90 are stacked fromoutside to inside of the tire radial direction.

(3.2) Modified Example 2

FIG. 5 is a partially enlarged sectional view of the run flat tire 10 B.As shown in FIG. 5, the run-flat tire 10 B, like the run-flat tire 10,includes the carcass reinforcing belt 50, the reinforcing layer 80, andthe width direction treat 90.

In the run flat tire 10 B, the width direction treat 90, the carcassreinforcing belt 50 and the reinforcing layer 80 are stacked fromoutside to inside of the tire radial direction.

(3.3) Modified Example 3

FIG. 6 is a partially enlarged sectional view of the run flat tire 10 C.As shown in FIG. 6, the run-flat tire 10 C, like the run-flat tire 10,includes the carcass reinforcing belt 50, the reinforcing layer 80, andthe width direction treat 90.

In the run flat tire 10 C, the width direction treat 90, the reinforcinglayer 80 and the carcass reinforcing belt 50 are stacked from outside toinside of the tire radial direction.

(4)Function and Effects

Next, the function and effects of the run flat tires 10, 10 A to 10 Cwill be described. In the run flat tires 10, 10 A to 10 C, the sidereinforcing rubber 70 is provided in the tire side portion 30, and thecarcass reinforcing belt 50, the reinforcing layer 80 and the widthdirection treat 90 are provided in layers at the inside of the treadportion 20 in the tire radial direction.

Therefore, even in the case of not a standard crossing belt layer butthe carcass reinforcing belt 50 in which the circumferential directioncord 51 is covered with a rubber material and the sheet-like reinforcinglayer 80 formed of a resin material, the side reinforcing rubber 70 caneffectively suppress buckling during run flat traveling.

In the run flat tires 10, 10 A to 10 C, the carcass reinforcing belt 50,the reinforcing layer 80 and the width direction treat 90 are providedin layers, so that failure of the carcass reinforcing belt 50 caused byoverriding a sharp projection or the like of a road surface can be moresurely prevented.

More specifically, since the carcass reinforcing belt 50 formed bycovering the circumferential direction cord 51 with a resin material isprotected and reinforced by the reinforcing layer 80 and the widthdirection treat 90, the bending deformation of the carcass reinforcingbelt 50 during run-flat traveling and the failure caused by the bendingdeformation can be suppressed.

That is, with the run flat tires 10, 10 A to 10 C, the suppression ofthe buckling and the failure prevention of the carcass reinforcing belt50 can be made compatible in a high dimension.

In particular, in the case of a structure in which the carcassreinforcing belt 50 is sandwiched by the reinforcing layer 80 and thewidth direction treat 90, such as the run flat tire 10 and the run flattire 10 B, the reinforcing layer 80 and the width direction treat 90function as reinforcing materials for the carcass reinforcing belt 50,but since the distance between the reinforcing layer 80 and the widthdirection treat 90 in tire radial direction can be secured, the in-plane(cross section along tire width direction and tire radial direction)rigidity when the carcass reinforcing belt 50, the reinforcing layer 80and the width direction treat 90 are integrally captured can beincreased.

Thus, the durability against the failure of the carcass reinforcing belt50 caused by overriding a sharp projection or the like of a road surfaceis greatly improved, and the run-flat traveling distance is alsolengthened.

The durability against the failure of the carcass reinforcing belt 50 ishigher when the width direction cord 91 included in the width directiontreat 90 is made of steel than Kevlar or the like. Further, as the angleformed by the width direction cord 91 with tire width directionapproaches 60 degrees, the cornering force tends to rise and thecornering power increases.

In addition, when the carcass reinforcing belt 50, the reinforcing layer80 and the width direction treat 90 are stacked from outside to insideof the tire radial direction as in the run flat tire 10 A, thedurability to the failure of the carcass reinforcing belt 50 is greatlyimproved.

Note that the run-flat tire 10 C exhibits intermediate performance(however, depending on the angle and material of the width directioncord 91) in terms of durability against failure of the carcassreinforcing belt 50 and the run-flat traveling distance as compared withthe run-flat tire 10 and the run-flat tire 10 B.

(5) Other Embodiments

Although the contents of the present invention have been described abovewith reference to the examples, it will be obvious to those skilled inthe art that the present invention is not limited to these descriptionsand that various modifications and improvements are possible.

For example, the width direction treat 90 provided in the run-flat tire10 may not necessarily be provided.

FIG. 7 is a partially enlarged sectional view of the run-flat tire 10 Daccording to another embodiment. As shown in FIG. 7, the run-flat tire10 D is provided with the reinforcing layer 80 compared with therun-flat tire 10 or the like, but is not provided with the widthdirection treat 90.

That is, in the run flat tire 10 D, the side reinforcing rubber 70 isprovided in tire side portion 30, and the carcass reinforcing belt 50and the reinforcing layer 80 are provided in layers on the inside intire radial direction of the tread portion 20.

In the run-flat tire 10 D, since the side reinforcing rubber 70 isprovided, even when the carcass reinforcing belt 50 in which thecircumferential direction cord 51 is covered with a rubber material andthe sheet-like reinforcing layer 80 formed of a resin material areprovided, the buckling can be more surely restrained.

While embodiments of the invention have been described as above, itshould not be understood that the statements and drawings which formpart of this disclosure are intended to limit the invention. Variousalternative embodiments, examples and operating techniques will becomeapparent to those skilled in the art from this disclosure.

REFERENCE SIGNS LIST

10, 10 A to 10 D Run-flat tire

20 Tread portion

30 Tire side portion

40 Carcass

41 Carcass cord

50 Carcass reinforcing belt

51 Circumferential direction cord

60 Bead portion

61 Bead Core

62 Bead filler

70 Side reinforcing rubber

80 Reinforcing layer

90 Width direction treat

91 Width direction cord

100 Rim wheel

110 Flange portion

1. A run-flat tire comprising: a tread portion in contact with a roadsurface; a tire side portion continuous to the tread portion andpositioned inside in a tire radial direction of the tread portion; and acarcass that forms tire skeleton, wherein a side reinforcing rubber isprovided in the tire side portion, and on an inner side of a tire radialdirection of the tread portion, a carcass reinforcing belt in which acircumferential direction cord extending along tire circumferentialdirection is covered with a rubber material and a sheet-like reinforcinglayer formed of a resin material are provided in a layer.
 2. The runflat tire according to claim 1, further comprising a width directiontreat formed by covering a width direction cord extending to the tirewidth direction with a rubber material inside the tire radial directionof the tread portion.
 3. The run-flat tire according to claim 2, whereinthe reinforcing layer, the carcass reinforcing belt and the widthdirection treat are stacked from outside to inside of the tire radialdirection.
 4. The run-flat tire according to claim 2, wherein the widthdirection treat, the carcass reinforcing belt and the reinforcing layerare stacked from outside to inside of the tire radial direction.
 5. Therun-flat tire according to claim 2, wherein the width direction treat,the reinforcing layer and the carcass reinforcing belt are stacked fromoutside to inside of the tire radial direction.
 6. The run-flat tireaccording to claim 2, wherein the carcass reinforcing belt, thereinforcing layer and the width direction treat are stacked from theoutside to inside of the tire radial direction.
 7. The run-flat tireaccording to claim 2, wherein an angle formed by the width directioncord and the tire width direction is 0 degrees or more and 60 degrees orless.